Autonomous underwater gliders are well-established sensing systems for long-range (trans-oceanic), deep (>1000 m), and long-endurance (several months) oceanographic data collection. These craft move through the water using variable buoyancy to initiate a climb/descent through the water column. By balance of hydrodynamic forces and moments, wing surfaces provide lifting force that transfers some of the vertical motion into horizontal translation. This means of locomotion is extremely efficient, and small underwater gliders have been demonstrated crossing entire oceans. However, underwater gliders are typically limited in top-speed to approximately 30 cm/s for cruise speed, with larger gliders reaching almost 1 m/s.
However, when rapid response is required, or when traversing over high current areas that would otherwise be unreachable by a conventional underwater glider, other means of propulsion is desirable.